A polar+equatorial wind model for broad absorption line quasars

I. Fitting the C IV BAL profiles

Institut d'Astrophysique et de Géophysique, University of Liège, Allée du 6 Août 17, 4000 Liège, Belgium e-mail: b.borguet@ulg.ac.be

Received: 7 September 2009
Accepted: 17 February 2010

Abstract

Context. Despite all the studies, the geometry of the wind at the origin of the blueshifted broad absorption lines (BAL) observed in nearly 20% of quasars still remains a matter of debate.

Aims. We want to see if a two-component polar+equatorial wind geometry can reproduce the typical BAL profiles observed in these objects.

Methods. We built a Monte Carlo radiative transfer code (called MCRT) to simulate the line profiles formed in a polar+equatorial wind in which the photons, emitted from a spherically symmetric core are resonantly scattered. Our goal is to reproduce typical C iv line profiles observed in BAL quasars and to identify the parameters governing the line profiles.

Results. The two-component wind model appears to be efficient in reproducing the BAL profiles from the P Cygni-type profiles to the more complex ones. Some profiles can also be reproduced with a pole-on view. Our simulations provide evidence of a high-velocity rotation of the wind around the polar axis in BAL quasars with non P Cygni-type line profiles.